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(No Model.) I

S. WATERS.

ELECTRIC LAMP.

Patnted Oct. 3, 1882.

WITNESSES INVENTOR:

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NI'IED STATES ATENT @rrrcn.

ELECTRIC LAMP.

SPECIFICATION forming part of Letters Patent No. 265,475, dated October3, 1882.

' Application filed May 3, 1882. (No model.)

To all whom it may concern Be it known that I, SIDNEY WATERs, of London,England, have invented certain new and useful Improvements in ElectricLamps, of which the following is a specification.

The object of my invention is to increase the illuminating-power ofelectriclamps, more particularly of incandescent lamps, and at the sametime give a more pleasing effect. To this end I form one-half (more orless) of the globe or flask of the lamp into a concave mirror by coatingthe glass externally with silver by chemical action or deposition.

In carrying out my invention I take a solution of nitrate of silver andprecipitate the silver with Rochelle salt, (tartrate of potash and ofsoda.)

After washing the precipitate thus obtained I mix it with an amount ofammonia which is almost, but not quite, sufficient to dissolve it, butwill leaveit in a milky state. Into this solution or liquor I immerse somuch of the lamp globe or flask as it is desired to coat with silver,the globe or flask having been previously fitted with its carbonfilament, exhausted, and sealed. 7 I then heat the solution by sendingan electric current through the lamp, and the silver is thus caused tobe deposited upon the exterior of the immersed portion of the globe. Toprevent as much as possible the deposit of silver upon the surface ofthe vessel containing the solution I sometimes cool it by any suitablemeans while the electric current is heating the lamp itself. In caseswhere it is not practicable to obtain the requisite heat by sending acurrent through the lamp-as, for instance, when the part to be coated isthe upper portion where the electric connections would be immersed inthe liquid, and in consequence decompose it, I apply the requisite heatto the "essel in which the solution is contained; but I avoid thismethod when possible, as it causes a deposit of silver upon the vesselas well as upon the lamp-globe.

In the accompanying drawings, Figure 1 is a side elevation of anelectric lamp treated according to my invention; and Fig. 2 is a sectionof the bath, showing in elevation two lamps undergoing treatment.

A is the glass bulb or flask of the lamp. B is the incandescentfilament, and the shaded portion 0 is designed to represent the depositof silver.

D is the bath of silver, contained in a tank or vessel, E, which is oneform that may be 5 gused for the purpose.

In Fig. 2 the terminals of the lamp are shown as connected to wires toa, which lead to the respective poles of a battery or electric-currentgenerator.

The particular portion of the globe which is formed into a mirror willdepend upon the position in which the lamp is intended to be used. Forexample, it the lamp is to be placed against a wall, the part or half ofthe globe nearest the wall will be formed into a mirror, as shown inFig. 1. To apply the mirrored surface to this portion of the lamp, thelatter is arranged on its side in the bath, as shown at the left in Fig.2; or, if the lamp is to be used overhead, the upper portion will beconverted into a mirror. This may be done by immersing the lamp, asshown at the right in Fig. 2, if it is to be used in a position invertedrelatively to Fig. 1.

In order to prevent a dark shadow being thrown on the wall behind or onthe. ceiling above the lamp, the deposit of silver is made so thin as tobe (liaphanous or notquite opaque, so that it will not entirely reflectthe light, but will permit a small portion of it to be transmitted.

My invention possesses the advantages over other methods of making aportion of the globe of an electric lamp into a concave mirror that thecoating is not liable to become dissipated in course of time, owing tothe heater the lamp when in use, and that, as already stated, it permitsthe passage through the mirror of sufficient light to avoid throwing ashadow. The process of treating the lamps is also simple and readilyeffected, and the applied coating does not mar the appearance of thelamp. The coating may be covered with varnish or other suitableprotective material.

\Vhat I claim is- The mode or process of coating part of the exterior ofthe globe of an electric lamp, which consists in immersing the part tobe coated in a solution of silver, and then sending an electric currentthrough the carbon filament of the lamp to produce the necessary heatfor causing a deposit of silver on the immersed part of the globe,substantially as set forth.

In witness whereof. I have hereunto signed my name in the presence oftwo subscribing witnesses.

SIDNEY WVATERS. Witnesses:

GEORGE O. BACON, ROBERT JAMES ISHERWOOD.

ICC

